This invention relates to a filter pit. In particular, the invention concerns a filter pit normally situated below ground and used to filter water collected from a catchment area and for directing the water to a storage tank.
In a typical water catchment, storage and distribution system, water is collected in a catchment area such as the roof of a building and directed to an in-ground filter pit by roof gutters and downpipes in which debris is removed from the water. The filtered water is directed from the filter pit and either directly to a storage tank or into the tank via a first flush water diverter. The water within the tank may then be distributed for consumption or use and is either pumped from the tank for immediate use or is pumped from the storage tank to a header tank from which it is then distributed for consumption/use.
Filter pits are usually constructed from plastic or concrete but plastic is preferred. The pit has one or more inlets adjacent an upper region of the pit and one or more outlets through which water may pass. The pit has a removable cover and a screen is located within the pit and water must pass through the screen as it travels from the inlet/s to the outlet/s. Typically, the screen has a mesh size of about 955 microns. A junk basket is suspended above the screen and is effective in preventing the passage of larger debris. Typically the junk basket has 6 mm apertures.
The pits are constructed in two sizes; 700 mm×700 mm×700 mm and 560 mm×560 mm×510 mm.
In the present water catchment, storage distribution systems and filter bags made of suitable material are positioned within the tank and are adapted to filter out fine particles of a size which pass through screen and junk basket from in the tank.
These filter bags were suspended within the storage tank and often were immersed in the water within the tank. In such cases, not only did the filter bag remain wet, the fines trapped by the bag were able to decompose and leach into the water in the tank and thereby contaminate the water.